1. Field of the Invention
The present invention relates to a circuit interrupter for performing arc extinction by puffing a fluid for arc extinction, such as SF.sub.6 gas. More particularly, it relates to a self arc extinction type circuit interrupter in which high pressure fluid whose pressure is raised by an arc formed between a pair of contacts is used for performing the arc extinction.
2. Description of the Prior Art
In conventional circuit interrupters, a fluid in a suitable volumetric space is pressurized by the pressurizing effect of arc energy transmitted from the arc to the fluid, and the pressurized fluid is released from an opening closed by the arc through the arc space under periodical change of the arc current, and the arc extinction is attained by the resulting puffing effect and cooling effect of the pressurized fluid.
In such self arc extinction type circuit interrupters, it is clear that the pressurizing function is important and indispensable. The pressurizing function is dependant upon the arc energy. Accordingly, the pressurizing function can be easily obtained in a zone having a large arc current, whereas it is difficult to obtain the pressure required for the arc extinction in a zone having a small arc current because the arc energy is significantly small and the pressurizing function is low. Accordingly, there is a zone for a significantly small arc extinction. This phenomenon is a serious disadvantage for using such circuit interrupters in high voltage fields, though it has a significant advantage in large current fields.
In order to effectively imparting the puffing effect and the cooling effect given by releasing the high pressure source onto the arc zone or area, it is necessary to rapidly discharge the arc energy provided in the arc space without leaving the fluid in the arc space too long and to prevent excessive elevation of the temperature of the fluid in the arc space, thereby preventing ionization of the fluid by the arc.